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/*
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 * Copyright (c) 2013, Stephen Colebourne & Michael Nascimento Santos
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  * Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
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 *  * Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
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 *  * Neither the name of JSR-310 nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
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package java.time.chrono;

import java.time.DateTimeException;
import java.time.temporal.ChronoUnit;
import java.time.temporal.Temporal;
import java.time.temporal.TemporalAmount;
import java.time.temporal.TemporalUnit;
import java.time.temporal.UnsupportedTemporalTypeException;
import java.util.List;
import java.util.Objects;

/**
 * A date-based amount of time, such as '3 years, 4 months and 5 days' in an
 * arbitrary chronology, intended for advanced globalization use cases.
 * <p>
 * This interface models a date-based amount of time in a calendar system.
 * While most calendar systems use years, months and days, some do not.
 * Therefore, this interface operates solely in terms of a set of supported
 * units that are defined by the {@code Chronology}.
 * The set of supported units is fixed for a given chronology.
 * The amount of a supported unit may be set to zero.
 * <p>
 * The period is modeled as a directed amount of time, meaning that individual
 * parts of the period may be negative.
 *
 * @implSpec This interface must be implemented with care to ensure other classes operate correctly.
 * All implementations that can be instantiated must be final, immutable and thread-safe. Subclasses
 * should be Serializable wherever possible.
 * @since 1.8
 */
public interface ChronoPeriod
    extends TemporalAmount {

  /**
   * Obtains a {@code ChronoPeriod} consisting of amount of time between two dates.
   * <p>
   * The start date is included, but the end date is not.
   * The period is calculated using {@link ChronoLocalDate#until(ChronoLocalDate)}.
   * As such, the calculation is chronology specific.
   * <p>
   * The chronology of the first date is used.
   * The chronology of the second date is ignored, with the date being converted
   * to the target chronology system before the calculation starts.
   * <p>
   * The result of this method can be a negative period if the end is before the start.
   * In most cases, the positive/negative sign will be the same in each of the supported fields.
   *
   * @param startDateInclusive the start date, inclusive, specifying the chronology of the
   * calculation, not null
   * @param endDateExclusive the end date, exclusive, in any chronology, not null
   * @return the period between this date and the end date, not null
   * @see ChronoLocalDate#until(ChronoLocalDate)
   */
  public static ChronoPeriod between(ChronoLocalDate startDateInclusive,
      ChronoLocalDate endDateExclusive) {
    Objects.requireNonNull(startDateInclusive, "startDateInclusive");
    Objects.requireNonNull(endDateExclusive, "endDateExclusive");
    return startDateInclusive.until(endDateExclusive);
  }

  //-----------------------------------------------------------------------

  /**
   * Gets the value of the requested unit.
   * <p>
   * The supported units are chronology specific.
   * They will typically be {@link ChronoUnit#YEARS YEARS},
   * {@link ChronoUnit#MONTHS MONTHS} and {@link ChronoUnit#DAYS DAYS}.
   * Requesting an unsupported unit will throw an exception.
   *
   * @param unit the {@code TemporalUnit} for which to return the value
   * @return the long value of the unit
   * @throws DateTimeException if the unit is not supported
   * @throws UnsupportedTemporalTypeException if the unit is not supported
   */
  @Override
  long get(TemporalUnit unit);

  /**
   * Gets the set of units supported by this period.
   * <p>
   * The supported units are chronology specific.
   * They will typically be {@link ChronoUnit#YEARS YEARS},
   * {@link ChronoUnit#MONTHS MONTHS} and {@link ChronoUnit#DAYS DAYS}.
   * They are returned in order from largest to smallest.
   * <p>
   * This set can be used in conjunction with {@link #get(TemporalUnit)}
   * to access the entire state of the period.
   *
   * @return a list containing the supported units, not null
   */
  @Override
  List<TemporalUnit> getUnits();

  /**
   * Gets the chronology that defines the meaning of the supported units.
   * <p>
   * The period is defined by the chronology.
   * It controls the supported units and restricts addition/subtraction
   * to {@code ChronoLocalDate} instances of the same chronology.
   *
   * @return the chronology defining the period, not null
   */
  Chronology getChronology();

  //-----------------------------------------------------------------------

  /**
   * Checks if all the supported units of this period are zero.
   *
   * @return true if this period is zero-length
   */
  default boolean isZero() {
    for (TemporalUnit unit : getUnits()) {
      if (get(unit) != 0) {
        return false;
      }
    }
    return true;
  }

  /**
   * Checks if any of the supported units of this period are negative.
   *
   * @return true if any unit of this period is negative
   */
  default boolean isNegative() {
    for (TemporalUnit unit : getUnits()) {
      if (get(unit) < 0) {
        return true;
      }
    }
    return false;
  }

  //-----------------------------------------------------------------------

  /**
   * Returns a copy of this period with the specified period added.
   * <p>
   * If the specified amount is a {@code ChronoPeriod} then it must have
   * the same chronology as this period. Implementations may choose to
   * accept or reject other {@code TemporalAmount} implementations.
   * <p>
   * This instance is immutable and unaffected by this method call.
   *
   * @param amountToAdd the period to add, not null
   * @return a {@code ChronoPeriod} based on this period with the requested period added, not null
   * @throws ArithmeticException if numeric overflow occurs
   */
  ChronoPeriod plus(TemporalAmount amountToAdd);

  /**
   * Returns a copy of this period with the specified period subtracted.
   * <p>
   * If the specified amount is a {@code ChronoPeriod} then it must have
   * the same chronology as this period. Implementations may choose to
   * accept or reject other {@code TemporalAmount} implementations.
   * <p>
   * This instance is immutable and unaffected by this method call.
   *
   * @param amountToSubtract the period to subtract, not null
   * @return a {@code ChronoPeriod} based on this period with the requested period subtracted, not
   * null
   * @throws ArithmeticException if numeric overflow occurs
   */
  ChronoPeriod minus(TemporalAmount amountToSubtract);

  //-----------------------------------------------------------------------

  /**
   * Returns a new instance with each amount in this period in this period
   * multiplied by the specified scalar.
   * <p>
   * This returns a period with each supported unit individually multiplied.
   * For example, a period of "2 years, -3 months and 4 days" multiplied by
   * 3 will return "6 years, -9 months and 12 days".
   * No normalization is performed.
   *
   * @param scalar the scalar to multiply by, not null
   * @return a {@code ChronoPeriod} based on this period with the amounts multiplied by the scalar,
   * not null
   * @throws ArithmeticException if numeric overflow occurs
   */
  ChronoPeriod multipliedBy(int scalar);

  /**
   * Returns a new instance with each amount in this period negated.
   * <p>
   * This returns a period with each supported unit individually negated.
   * For example, a period of "2 years, -3 months and 4 days" will be
   * negated to "-2 years, 3 months and -4 days".
   * No normalization is performed.
   *
   * @return a {@code ChronoPeriod} based on this period with the amounts negated, not null
   * @throws ArithmeticException if numeric overflow occurs, which only happens if one of the units
   * has the value {@code Long.MIN_VALUE}
   */
  default ChronoPeriod negated() {
    return multipliedBy(-1);
  }

  //-----------------------------------------------------------------------

  /**
   * Returns a copy of this period with the amounts of each unit normalized.
   * <p>
   * The process of normalization is specific to each calendar system.
   * For example, in the ISO calendar system, the years and months are
   * normalized but the days are not, such that "15 months" would be
   * normalized to "1 year and 3 months".
   * <p>
   * This instance is immutable and unaffected by this method call.
   *
   * @return a {@code ChronoPeriod} based on this period with the amounts of each unit normalized,
   * not null
   * @throws ArithmeticException if numeric overflow occurs
   */
  ChronoPeriod normalized();

  //-------------------------------------------------------------------------

  /**
   * Adds this period to the specified temporal object.
   * <p>
   * This returns a temporal object of the same observable type as the input
   * with this period added.
   * <p>
   * In most cases, it is clearer to reverse the calling pattern by using
   * {@link Temporal#plus(TemporalAmount)}.
   * <pre>
   *   // these two lines are equivalent, but the second approach is recommended
   *   dateTime = thisPeriod.addTo(dateTime);
   *   dateTime = dateTime.plus(thisPeriod);
   * </pre>
   * <p>
   * The specified temporal must have the same chronology as this period.
   * This returns a temporal with the non-zero supported units added.
   * <p>
   * This instance is immutable and unaffected by this method call.
   *
   * @param temporal the temporal object to adjust, not null
   * @return an object of the same type with the adjustment made, not null
   * @throws DateTimeException if unable to add
   * @throws ArithmeticException if numeric overflow occurs
   */
  @Override
  Temporal addTo(Temporal temporal);

  /**
   * Subtracts this period from the specified temporal object.
   * <p>
   * This returns a temporal object of the same observable type as the input
   * with this period subtracted.
   * <p>
   * In most cases, it is clearer to reverse the calling pattern by using
   * {@link Temporal#minus(TemporalAmount)}.
   * <pre>
   *   // these two lines are equivalent, but the second approach is recommended
   *   dateTime = thisPeriod.subtractFrom(dateTime);
   *   dateTime = dateTime.minus(thisPeriod);
   * </pre>
   * <p>
   * The specified temporal must have the same chronology as this period.
   * This returns a temporal with the non-zero supported units subtracted.
   * <p>
   * This instance is immutable and unaffected by this method call.
   *
   * @param temporal the temporal object to adjust, not null
   * @return an object of the same type with the adjustment made, not null
   * @throws DateTimeException if unable to subtract
   * @throws ArithmeticException if numeric overflow occurs
   */
  @Override
  Temporal subtractFrom(Temporal temporal);

  //-----------------------------------------------------------------------

  /**
   * Checks if this period is equal to another period, including the chronology.
   * <p>
   * Compares this period with another ensuring that the type, each amount and
   * the chronology are the same.
   * Note that this means that a period of "15 Months" is not equal to a period
   * of "1 Year and 3 Months".
   *
   * @param obj the object to check, null returns false
   * @return true if this is equal to the other period
   */
  @Override
  boolean equals(Object obj);

  /**
   * A hash code for this period.
   *
   * @return a suitable hash code
   */
  @Override
  int hashCode();

  //-----------------------------------------------------------------------

  /**
   * Outputs this period as a {@code String}.
   * <p>
   * The output will include the period amounts and chronology.
   *
   * @return a string representation of this period, not null
   */
  @Override
  String toString();

}
